The present invention relates to bobbin magazines for use with a travelling service device for servicing operating stations of a yarn processing machine. The invention is intended particularly, but not exclusively, for use in connection with travelling doffers for open-end spinning machines, for example rotor spinning machines.
Travelling doffers for use on rotor spinning machines are now very well known, being offered virtually as standard equipment on the rotor spinning machines exhibited at the International Textile Machinery Exhibition held in Milan, Italy in October 1983. It is therefore believed unnecessary to provide a detailed description of such doffers here. Broadly, their function is to patrol back and forth past the individual spinning stations of the rotor spinning machine and, when a yarn package of predetermined size has been produced at one particular spinning station, to stop in front of that spinning station, transfer the completed package from the package holder of the spinning station to a suitable package transporting means, (for example a conveyor belt extending longitudinally of the central portion of the machine) and to insert a fresh bobbin tube into the package holder of the spinning station so that yarn newly spun at that spinning station can be wound up on the fresh bobbin tube.
Various systems have been proposed for providing a fresh bobbin tube in readiness for a doffing operation. The present invention relates to systems in which the travelling doffing device carries its own bobbin magazine so that during its patrolling movements the doffing device carries a stock of bobbin tubes, the maximum size of which is limited only by the capacity of the magazine.
It is normally relatively easy to provide a bobbin magazine for a rotor spinning machine which produces cylindrical packages or "cheeses". These are produced on cylindrical bobbin tubes which can be made to roll in a substantially predetermined fashion in and from the magazine. Furthermore, such bobbin tubes can be made substantially symmetrical about their middle section so that there is no left-hand/right-hand problem during the transfer of a bobbin tube to a spinning station. Accordingly, there is generally no need to provide complicated feed equipment in association with magazines for cylindrical bobbins, and the available space on the doffer can be used efficiently for bobbin storage.
However, problems arise when the rotor spinning machine produces frusto-conical ("conical") packages which are produced on correspondingly conical bobbin tubes. Such conical tubes do not roll in a readily controllable manner, and they must be inserted into the spinning station with a specific longitudinal orientation. A bobbin magazine for conical bobbins is therefore generally more complex than a magazine for cylindrical bobbins, and a given amount of storage space can generally be used less efficiently for conical bobbins than for cylindrical bobbins. This can be of a special importance where a travelling doffer is designed to be adaptable for use selectively with cylindrical or conical packages.
When the rotor spinning machine performs its normal operation, doffing operations will be called for at some statistically calculable average frequency so that the capacity of the doffer magazine is sufficient for a corresponding period of operating time. However, the doffer may also be designed for multipurpose operation, and in particular for automatic start-up of the machine. In such circumstances all of the package holders in the spinning machine may be empty at the beginning of the start-up operation and the doffer may be required to insert a bobbin tube into the package holder of each spinning station in succession as a part of its start-up sequence at that station. The frequency of demand for fresh bobbins tubes will be much higher during the start-up operation than during normal operation, and the capacity of the magazine which is adequate for normal operation may produce a very long start-up operation for the machine as a whole due to the need for frequent topping-up or filling of the bobbin magazine. Proposals have therefore already been made to use sticks of telescoped or nested conical bobbin tubes to improve efficiency of space utilization in bobbin magazines. U.S. Pat. No. 4,066,218 proposes a system in which a bobbin magazine on the doffer consists of a single stick of telescoped tubes, and an automatic loading device provided at one end of the machine comprises an elevator adapted to receive a plurality of sticks of tubes and to transfer them one by one to the doffer magazine as and when called for. The axes of the bobbin tubes are aligned along the length of the machine in both the doffer magazine and the loading station elevator.
German Published Patent Application No. 2,131,957 describes a doffer magazine in which a plurality of sticks of telescoped bobbin tubes can be mounted in respective compartments of a carousel-like device rotatable about an axis parallel to the axes of the bobbin tubes in the sticks. The device can be rotated to bring the sticks successively into alignment with a separating station at which individual tubes can be separated from the stick currently aligned with the separating station. The mounting of this magazine in the doffer is not shown, but the sticks of tubes are disposed vertically in the magazine, and accordingly the individual tubes would normally have to be re-oriented after leaving the magazine before insertion in a spinning station in which the bobbin axes are normally disposed horizontally. Accordingly, neither of the above publications shows a simple system providing for an efficient use of the available storage space.